Electrical measuring device



Feb. 21, 1950 J. a. SHAW 2,497,961

ELECTRICAL MEASURING DEVICE Filed Jan. 17, 1946 JNVENTOR. Jose M! QS/an/ATTYS Patented Feb. 21, 1950 U NITED STATES PATENT OFFICE ELECTRICALMEASURING DEVICE J osephD. Shaw, CincinnatLOhio Application January 17,1946, Serial No. 641,696

4 Claims.

The present invention relates to electrical measuring devices and isparticularly directed to a means for increasing theaccuracy of devicesfor indicating or measuring voltages.

It is an object of this invention to provide a device for materiallyincreasing the range of conventional voltmeters and also to improve thenet accuracy of voltage indicators b automatically balancing out byknown opposition voltages a sufficient portion-of the unknown voltage sothat the remaining unbalanced portion of the unknown voltage is withinthe range of such conventional meters.

Another object of the invention is to provide a completely automatic andaccurate device for measuring the value of unknown voltages.

A further object of the invention is to provide a voltage measuringdevice which automatically and successivel introduces into theopposition circuit of the unknown voltage a number of resistors havingequal, predetermined impedance values, until the opposition circuit isin a substantially balanced condition.

A still further object of the invention is to provide in a voltagemeasuring device having the foregoing characteristics, an automaticmeans for adjusting the device in accordance with the polarity of theunknown voltage which applies in opposition to the unknown, polarizedvoltage a known voltage of opposite polarity.

Other objects will be apparent from the following specification anddrawing wherein the figure is a wiring diagram of my electricalmeasuring device, the mechanical parts being shown in front elevation.

In the drawing the reference numeral 2 indicates a source of unknownvoltage which may have a high internal resistance. The negativeconductor 3 of :this voltage source is normally connected in series witha pair of stepping relays and 5 through a double'throw, single poleswitch 5 comprising one of a series of similar switches actuatedsimultaneously by an armature 7 of a polarity reversing relay. Thestepping relays 4 and 5 have a number of resistors 8 and 9 respectivelywhich are arranged .in series and have interposed betweenthem a circularrow of taps I and II respectively. Movable switch arms I2 and I3 arerotatably mounted concentric with the rows or taps I 0 and I Irespectively, and are automaticall actuated by certain relays toconsecutively include or exclude resistors from an opposition circuit tothe unknown voltage 2.

The opposition circuit comprises the negative terminal 3 which isconnected in series with the stepping relays 4 and by means of a line I4having the switch 6 interposed therein. This line is connected to theZero tap I5 oftherow I9, and the circuit may-pass through switch arm [2or through one or more of the resistors S-and thence to the switch armI2 of the stepping relay 4, depending upon the setting of said arm. Theswitch arm I2 is connected to the zero tapIG'of the row II for steppingrelay 5 by a line I1, the switch arm I3 of the latter relay beingconnected tothe grid I8 of a thermionictube I9 by-a'line 29 which hasinterposed therein a battery ZI and a double throw, single pole switch22 actuated by armature -'l. The cathode23 of the tube is connected tothe positive terminal 24 of the unknown voltage source by an electricalconnection with line 25.

Batteries 26- and 2! supply current to theser-ies of resistors 8 and 9respectively, the negative terminals of said batteries being connectedto zero taps Hand 56 respectivelyso that the voltages across 8 and 9 areplaced in opposition to the unknown voltage source and create anopposition circuit therefor. It will thereforebe noted that apotentialdifference will exist between electrical points 28 and 29 in lines 25and 7.9 respectively when the total voltage occurring between point I5and=switch arm I2 plus the voltage occurring between point it and switcharm I-3 does not balance out the unknown voltage 2.

The potential across the resistors 8 and that across the resistors 9 mabe accurately adjusted to a definite Value'by means of rheostats-llfland3| placed in series in the circuits of batteries 26 and?! respectively.

It is contemplated that the potential difference acrosseach'of theresistors 8 may be the equivalent of one-volt and that the potentialdifference across each resistor 9 may be equal to one-tenth volt,thereby giving the entire row of resistors9 the total potentialdifference of nine-tenths volts.

When the unknown voltage 2 becomes greater than the balancing voltagesof stepping relays 4 and 5, grid I8 of tube I9 becomes sufiiciently morenegative than normal bias with respect to its cathode 23 and causes thecurrent to decrease in'the plate circuit comprising battery 32,polarized relay coils 33 and 34, and thermionic tube plate 290. Whenthis current is of a sufficiently low value a normally closed switch 35of relay 33 is closed. Relay 33 is adjusted so that switch 35 closeswhen the potential of point 29 is more negative than that of point 28 byan amount somewhat greater than the potential difference occurringacross one of the resistors 9.

As has been stated above relay switch 35 is adapted to close and engagecontact 35 when the voltage across the unknown source 2 is greater thanthe voltage across the points 28 and 29 by an amount specified above,and the point 29 is negative with respect to the positive terminal 24.This switch action causes operation of the stepping relay mechanisms toautomatically include in the opposition circuit a greater number ofresistors and hence a greater countervoltage until the required part ofthe unknown voltage is balanced out thereby. However, in the event point29 is more positive than the positive terminal 24, the plate circuit ofthe tube |9 will cause the normally opened relay 34 to move switch arm31 into engagement with contact 38 and cause the stepping relaymechanisms to exclude successive resistors from the opposition circuit.

In the first instance when the switch arm 35 engages the contact 36, acircuit to relay 39 is closed, said circuit comprising a source of power49, master switch 4|, line 42, switch 35, contact 36, line 43, switch44, line 45, switch 46, line 41, relay 39, and power lines 489 and 48.Actuation of the relay 39 closes lock switch 49 and also switch 59 whichinstitutes actuation of the timer said timer receiving power from source49 by lines 52 and 53. Actuation of relay 39 also opens switch 54 thuspreventing actuation of relay 55 until the cycle initiated by theactuation of relay 39 is completed. Master switch 4| is normally closedand upon actuation of the timer 5| said switch remains closed until itis opened by said timer after a period of time. Said timer then holdssaid switch open for a period of time and then returns said switch tonormally closed position. When master switch 4| is opened by the timer5|, relay 39 is no longer actuated and lock switch 49 opens. Afterswitch 4| is again closed by the timer, relay 39 does not close unlessswitch engages contact 36.

.Now, assuming that the stepping relays are in zero positions, it willbe noted that actuation oithe relay 39 also closes switch 559 whichconnects power source 49 through switch 46 and switch 4| to a solenoid56 by line 51 which has also in series therewith a double throw, singlepole switch 58. The opposite side of the solenoid 56 is connected to thesource of power 49 by lines 59,69, GI, 62 and 48. Upon actuation of thesolenoid 56 movement of the armature therefor advances a ratchet wheel63 of the stepping relay 5 one notch and the associated arm I3 isadvanced to the next succeeding tap thereby bringing into the oppositioncircuit an additional resistor 9. After a predetermined interval of timethe timer 5| opens master switch 4| thereby deenergizing solenoid 56 andallowing its armature to return to neutral position (shown in thedrawing) for engagement with the next succeeding notch on the wheel 63upon the reception of the next electric impulse from the power source49. The foregoing cycle is repeated until either sufiicient balanceobtains between the unknown voltage source 2 and the opposition circuit(i. e. arm 35 no longer engages contact 36) or until the arm [3 advancesclockwise to a point where an arm of switch 64 is urged into engagementwith the lower contact, whereupon a relay 65 is powered by battery 66.This brings switch 58, which normally engages the upper contact, intoengagement with the lower contact thus connecting solenoid 61 throughline 619 to line 51. The opposite side of solenoid 61 is connected topower source 49 by lines 68, 69, 6|, 62, and 48. Relay 65 is of the timedelay type so that arm 58 does not engage the lower contact after theinitial actuation of relay 65 until master switch 4| has been opened bythe timer 5|. Th solenoid 61 continues to advance ratchet wheel 19 inthe same manner that solenoid 56 advanced ratchet wheel 63 until thecircuit is balanced sufliciently that arm 35 no longer engages contact36. The total reading of the stepping relays 4 and 5 plus the unbalancedfraction in the circuit indicated on a volt meter 1| gives the accuratevoltage of the unknown source 2. It is contemplated that the range ofvoltmeter 1| should be greater than the sum of the minimum numericalvalue of the potential difference that must occur between points 28 and29 in order that arm 35 contacts 36 plus the minimum numerical value ofthe potential difference that must occur between 28 and 29 in order that31 contacts 38.

In the event the point 29 is more positive than the positive terminal 24and therefore if the circuit is in a sufficiently unbalanced condition,the arm of normally open relay 31 will engage contact 38 which closesthe relay 55. To this end the source of power 49 is connected throughmaster switch 4| to line 42, switch arm 31, contact 38, line 12, switch13, line 14, switch 54, line 15, relay 55, line 16, line 11 and line 48.In addition actuation of relay 55 opens switch 46 thus preventingactuation of relay 39 until the cycle initiated by the actuation ofrelay 55 is completed.

Upon actuation of the relay 55, the locking switch 18 and the timerswitch 19 are closed. Timer switch 19 thus initiates operation of thetimer 5|. This action also closes switch 89, which connects solenoid 8|to power source 49 through switches 4|, 18, 54, 89, line 94, switch 869,and line 95. The opposite side is connected to power source 49 throughlines 6|, 62, and 48. This permits the ratchet wheel 63 to movecounterclockwise one notch under the bias of a coil spring 82. Thisprocess continues until the circuit is substantially balanced (i. e.until arm 31 no longer engages contact 38) or until the arm |3 engagesnormally open switch arm 83. The closing of switch 83 actuates relay 84by power supplied by battery 85. Relay 84 is a time delay relay with aperiod of delay such that it brings switch 869 into engagement with itslower contact after timer 5| has opened switch 4|. A solenoid 85 isconnected to the power source 49 by switch 92, line 96, switch 869, line94, switches 89, 54, 18, and 4|. The opposite side of solenoid 86connects to power source 49 by lines 68, 69, 6|, 62, and 48. In theevent substantial balance has not been attained in the oppositioncircuit, solenoid 86 of stepping relay 4 is brought into operation whichactuates the ratchet wheel 19 to move the arm l2 counterclockwise underthe action of a coil spring 88 in the same manner that solenoid 8|permitted l3 to move counterclockwise and until the circuit issubstantially balanced, or until the arm l2 closes switch 89. Thiscauses a relay 99 to be actuated by power supplied by battery 9|. Relay99 is of the time delay type with a period such that it moves a switch92 into engagement with its lower contact after timer 5| has openedswitch 4|.

If arm 31 is in engagement with contact 38 after arm |2 has moved topoint l5 and switch 92 is in contact with its lower contact, relay 1receives an impulse of current from power source 49 through switch 92,line 96, switch 869, line 94, switches 89, 34, 18, and 4|. The oppositeside of relay 1 connects to power source 49 by lines 62 and 48. Relay 1is an impulse type relay which changes the positions of switches 22, 6,93, 13 and 44 whenever it receives an impulse. Thus when actuated asdescribed it causes said switches to engage their right hand contactsand the device is prepared to measure unknown voltages of polarityopposite to that shown in the drawing. It will be noted that in saidreversed switch positions the switches 35 and 31 now control relays 55and 39 respectively. This circuit allows opposition voltages, producedby stepping relays 4 and 5, to be placed in the opposite direction tothat previously described. Switch 93 conditions voltmeter 1| to measurevoltages of opposite polarity to that previously described. In the eventthat the unknown voltage returns to the polarity indicated above,switches 22, 6, 93, 73, and 44 will return to the positions shown in thedrawing and the device will again be prepared to measure voltages of thepolarity shown.

It will therefore be understood that switches 44, 13, 93, 6 and 22 andthe armature 7 which actuates said switches in unison when the armatureis energized serve to reverse the polarity of the opposition circuitwhen such reversal is necessary to balance the unknown voltage. For thisreason I have used the terms polarity reversin relay to designate thesearmature controlled switches in the claims.

What is claimed is:

1. An electric measuring device comprisin a source of unknown voltage, astepping relay having a number of resistors of predetermined and uniformvalues connected in series, a tap connected to the end of each resistor,and including a zero tap, said zero tap being connected to one terminalof the unknown voltage, a movable switch arm adapted to successivelyengage the taps, a source of known voltage connected across the seriesof resistors to constitute the known voltages applied by the steppingrelay and opposition circuit to the unknown voltage, actuating means forthe arm, relay means interposed in the opposition circuit between theswitch arm and the remaining terminal of the unknown voltage andresponsive to an unbalance in said circuit, means connecting the relaymeans with the arms actuating means to change the value of potentialdifference applied by the stepping relay, a polarity reversing relay inthe opposition circuit, and means actuated by the zero tap contactingposition of the stepping relay arm for operating the polarity reversingrelay.

2. An electric measuring device comprising a source of unknown voltage,a stepping relay having a number of resistors of predetermined anduniform values connected in series, a series of taps each connected toadjacent ends of the resistors, said series including a zero tapconnected to one terminal of the unknown voltage, a movable switch armadapted to successively engage the taps, an opposition circuit to theunknown voltage including a battery connected across the series ofresistors, advancing and retracting mechanism for the arm, a pair ofpolarized relays connected in the opposition circuit and responsive toan unbalance in said circuit, means connecting the polarized relays withthe advancing and retracting mechanism to respectively out in or out ofthe opposition circuit one or more of the said resistors untilsubstantial balance is attained between the unknown voltage and thevoltage in the opposition circuit, a polarity reversing relay in theopposition circuit, a meter connected across the terminals of theunknown voltage and actuated by the polarity reversing relay, and meansactuated by the zero tap contacting position of the stepping relay armfor operating the polarity reversing relay.

3. An electric measuring device comprising a source of unknown voltage,a stepping relay having a number of resistors of predetermined anduniform values connected in series, a tap connected to the ends of eachresistor including a zero tap at one end of the series connected to oneterminal of the unknown voltage, a movable switch arm adapted tosuccessively engage the taps, a source of known voltage connected acrossthe series of resistors to constitute the known voltages applied by thestepping relay and opposition circuit to the unknown voltage, advancingand retracting mechanism for the arm, a pair of polarized relaysresponsive to an unbalance in said circuit, means connecting thepolarized relays with the mechanism to change the value of potentialdifference applied by the stepping relay to substantially balance theunknown voltage in the opposition circuit, a polarity reversing relay inthe opposition circuit, and means actuated by the zero tap contactngposition of the stepping relay arm for operating the polarity reversingrelay.

4. An electric measuring device comprising a source of unknown voltage,a stepping relay having a number of resistors of predetermined anduniform values connected in series, a tap connected to the end of eachresistor, and including a zero tap, said zero tap being connected to oneterminal of the unknown voltage, a movable switch arm adapted tosuccessively engage the taps, a source of known voltage connected acrossthe series of resistors to constitute the known voltages applied by thestepping relay and opposition circuit to the unknown voltage, actuatingmeans for the arm, relay means interposed in the opposition circuitbetween the switch arm and the remaining terminal of the unknown voltageand responsive to an unbalance in said circuit, a potential indicatingdevice connected between the movable switch arm and the said remainingterminal of the unknown voltage, means connecting the relay means withthe arm actuating means to change the value of potential differenceapplied by the stepping relay, a polarity reversing relay in theopposition circuit, means actuated by the zero tap contacting positionof the stepping relay arm for operating the polarity reversing relay,and means actuated by the polarity reversing relay for interchanging theterminal connections of the potential indicating device.

JOSEPH D. SHAW.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Nuler Name Date 1,178,772 Zimmerman Apr. 11, 19161,438,947 Conway Dec. 19, 1922 1,696,415 Roberts Dec. 25, 1928 2,046,422Matte l July 7, 1936 2,062,915 Lamb Dec. 1, 1936 2,279,232 Graham Apr.7, 1942 2,321,605 Keinath June 15, 1943 2,384,167 Harrington et a1.Sept. 4, 1945 FOREIGN PATENTS Number Country Date 266,798 Great BritainFeb. 28, 1927 Certificate of Correction Patent N 0. 2,497,961 February21, 1950 JOSEPH D. SHAW It is hereby certified that errors appear in theprinted specification of the above numbered patent requiring correctionas follows Column 5, line 41, and column 6, lines 15 and 38, for thewords relay and read relay an; column 5, line 48, for arms reed mm;column 6, line 25, for conand that the said Letters Patent should beread with these 1; e same may conform to the record of the casein thePatent Office.

Signed and sealed this 30th day of May, A. D. 1950.

[sun] THOMAS F. MURPHY,

Assistant Uommz'asioner of Patents.

Certificate of Correction Patent N 0. 2,497,961 February 21, 1950 JOSEPHD. SHAW It is hereby certified that erro1 -s appear in the printedspecification of the above numbered patent requlrmg correctlon asfollows;:

Column 5, line 41, and column 6, lines 15 and 38, for the words relayand read relay an; column 5, line 48, for arms read arm; column 6, line25, for contactng read contacting;

[sun] THOMAS F. MURPHY,

Assistant Uommz'aaz'oner of Patents.

